Android图片压缩的实例详解

/** 
   * 按比例压缩图片分辨率 
   * @param inBitmap 
   * @param outHeight 输出图片高度，可据此保持比例计算输出宽度 
   * @param needRecycled 是否回收inBitmap 
   * @return 
   */ 
  public static Bitmap createScaledBitmapByOutHeight(Bitmap inBitmap, int outHeight, boolean needRecycled) {      
    int bitmapHeight = inBitmap.getHeight(); 
    int bitmapWidth = inBitmap.getWidth(); 
    int outWidth = bitmapWidth * outHeight / bitmapHeight; 
     
    return createScaledBitmap(inBitmap, outWidth, outHeight, needRecycled); 
  }  
   
  /** 
   * 按比例压缩图片分辨率 
   * @param inBitmap 
   * @param outHeight 输出图片宽度，可据此保持比例计算输出高度 
   * @param needRecycled 是否回收inBitmap 
   * @return 
   */ 
  public static Bitmap createScaledBitmapByOutWidth(Bitmap inBitmap, int outWidth, boolean needRecycled) {     
    int bitmapHeight = inBitmap.getHeight(); 
    int bitmapWidth = inBitmap.getWidth(); 
    int outHeight = bitmapHeight * outWidth / bitmapWidth; 
     
    return createScaledBitmap(inBitmap, outWidth, outHeight, needRecycled); 
  } 
   
  /** 
   * 指定输出的宽高缩放图片 
   * @param inBitmap 
   * @param outWidth 
   * @param outHeight 
   * @param needRecycled 
   * @return 
   */ 
  public static Bitmap createScaledBitmap(Bitmap inBitmap, int outWidth, int outHeight, boolean needRecycled) {         
     
    Bitmap thumbBmp = Bitmap.createScaledBitmap(inBitmap, outWidth, outHeight, true); 
    if (needRecycled) { 
      inBitmap.recycle(); 
    } 
     
    return thumbBmp; 
  } 

/** 
   * 从资源加载并压缩图片 
   * @param res 
   * @param resId 
   * @param outWidth 目标宽度 
   * @param outHeight 目标高度 
   * @return 
   */ 
  public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,  
      int outWidth, int outHeight) {  
    final BitmapFactory.Options options = new BitmapFactory.Options();  
    options.inJustDecodeBounds = true; // 假解,来获取图片大小  
    BitmapFactory.decodeResource(res, resId, options);  
    options.inSampleSize = calculateInSampleSize(options, outWidth, outHeight);  
    // 使用获取到的inSampleSize值再次解析图片  
    options.inJustDecodeBounds = false; 
    //options.inPreferredConfig = Config.RGB_565; 
    return BitmapFactory.decodeResource(res, resId, options);  
  }  
   
  /** 
   * 从文件中加载并压缩图片 
   * @param res 
   * @param resId 
   * @param outWidth 目标宽度 
   * @param outHeight 目标高度 
   * @return 
   */ 
  public static Bitmap decodeSampledBitmapFromFile(String pathName, int outWidth, int outHeight) { 
    final BitmapFactory.Options options = new BitmapFactory.Options();  
    options.inJustDecodeBounds = true; // 假解,来获取图片大小  
    BitmapFactory.decodeFile(pathName, options); 
    options.inSampleSize = calculateInSampleSize(options, outWidth, outHeight);  
    // 使用获取到的inSampleSize值再次解析图片  
    options.inJustDecodeBounds = false; 
    //options.inPreferredConfig = Config.RGB_565; 
    return BitmapFactory.decodeFile(pathName, options); 
  }  
   
  /** 
   * 计算options.inSampleSize 
   * @param options 
   * @param reqWidth 
   * @param reqHeight 
   * @return 
   */ 
  public static int calculateInSampleSize(BitmapFactory.Options options,  
      int reqWidth, int reqHeight) {  
    // 源图片的高度和宽度  
    final int height = options.outHeight;  
    final int width = options.outWidth;  
    int inSampleSize = 1;  
    if (height > reqHeight || width > reqWidth) {  
      // 计算出实际宽高和目标宽高的比率  
      final int heightRatio = Math.round((float) height / (float) reqHeight);  
      final int widthRatio = Math.round((float) width / (float) reqWidth);  
      // 选择宽和高中最小的比率作为inSampleSize的值，这样可以保证最终图片的宽和高  
      // 一定都会大于等于目标的宽和高。  
      inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;  
    }  
    return inSampleSize;  
  }  

/** 
   * 压缩图片质量，把图片压缩到outSize以内 
   * @param inBitmap 原始bitmap 
   * @param outSize 压缩到的大小 
   * @param needRecycled 是否回收bitmap 
   * @return 
   */ 
  public static Bitmap compressImage(Bitmap inBitmap, int outSize, boolean needRecycled) {  
      
    ByteArrayOutputStream baos = new ByteArrayOutputStream();  
    inBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos); 
    int quality = 100;  
    while (baos.toByteArray().length / 1024 > outSize) { 
      if (quality <= 0) { 
        ByteArrayInputStream outBais = new ByteArrayInputStream(baos.toByteArray()); 
        return BitmapFactory.decodeStream(outBais, null, null);// 如果quaLity为0时还未达到32k以内，返回得到的最小值;如需要可结合分辨率压缩 
      } 
      baos.reset(); 
      //PNG格式下，这种压缩不起作用（quality:0-100,如果目标大小太小，有时候质量压缩不一定能达到效果，需结合分辨率压缩） 
      inBitmap.compress(Bitmap.CompressFormat.JPEG, quality, baos); 
      Log.e("AN", "bitmap size:"+ baos.toByteArray().length / 1024 + "k"); 
      quality -= 10; 
    } 
    if (needRecycled) { 
      inBitmap.recycle(); 
    } 
     
     
    ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray()); 
    Bitmap outBitmap= BitmapFactory.decodeStream(bais, null, null);//ByteArrayInputStream转成bitmap 
     
    return outBitmap;  
  }